Fan



y 1939- K. D. MCMAHAN 2,160,667

. FAN

Filed April 1, 193a s sheets-sheet 1 Fig.1,

/ lfivefitorfl Kenton DMcMahan,

by 54:: Q

His Attorney.

FAN

my 30,1939. K. D. MCMAHAN -2.160,661

Filed April 1, i938 s Sheets-Sheet 2 FigA.

I Invefit'or: Kenton D.McMahan,

His Attorney.

May 30, 1939. MOMAHAN 2,160,667

FAN

Filed April 1, 195a 3Sheets-Sheet s 6 Inventor".

Kenton D .McM'ahafi.

' His Attorn ey.

Patented May 30, 1939 UNITED STATES.

PATENT OFFICE FAN New York Application April l, 1938, Serial No. 199,460

8 Claims. (or. 230-434) The present invention relates to centrifugal fans and is an improvement on my application Serial No. 82,780, filed June 1, 1936.

The object of my invention is to provide an improved construction in centrifugal fans which will have quiet and eflicient operation. For a consideration of what I believe to be novel and my invention, attention is directed to the following description and theclaims appended thereto.

In the accompanying drawings, Fig. 1 isa side elevation, partly broken away, of a dynamoelectric machine equipped with a fan embodying my invention; Fig. 2 is a perspective view of the fan; Fig. 3 is a front elevation of one of the fan blades; Fig. 4 is a rear elevation of one of the fan blades; Fig. 5 is a top plan view of one of the fan blades; Fig. 6 is a perspective view of one of the fan blades; Fig. '1 is a plan view of one of the fan blades; Fig. 8 is a sectional view taken on line 8--8 of Fig. 7 showing the blade shape with reference to a datum plane passing through the front end of the blade and inclined backwardly with respect to the rotation of the fan through an angle of the order of 30; Fig. 9 is a diagram matic view showing the blade shape along lines A-and B in Fig. '1 with respect to the same datum plane; Fig. 10 is a diagrammatic view showing the blade shape alonglines C and D in Fig. 7 with respect to the same datum plane; and Fig. 11 is a. diagrammatic view showing the blade shape along lines E and G with 'respect to the same datum p1ane.

Referring to the drawings, I have shown my :5 invention used as a ventilating fan for a dynamoelectric machine having a stationary, member I and a rotating member 2 carried in a frame 3. The stationary and rotating members are divided into two sections spaced apart along the longi- 40 tudinal axis of the machine. In the space be tween the sections is a hub I which comprises an annular ring fixed to the rotating member on opposite sides of which are carried axially extending fan blades 5. The rear ends 6 of the blades are fixed to annular rings 1 which are fixed to opposite faces of the hub. Shroud rings 8 are fixed to the outer portions of the front ends of the blades. The inner edges 9 of the blades de-- fine a passage through which air flows axially to the fan blades. The air is discharged radially from the outer edges ill of the blades. During the rotation of the fan, air is drawn axially into the inner edges of the fan and is discharged from the outer edges to a scroll casing II.

The blade shape and the arrangement of the so that adjacent the front ends, the blades are curved forwardly. This change in inclination is clearly shown in Figs. 8 and 11. The net result is that the front faces of the blades are concave in an axial direction.

The inner edges 9 of the blades, as shown in Figs. 3 and 7, are curved radially outward an increasing amount from the rear end toward the front end of the blades. The inner edges terminate in a forwardly curved end 12 which projects within the inner edge of the shroud ring 8. The forwardly curved ends l2 serve as scoops or as propeller fan elements which increase the axial flow of air to the fan. This increases the effectiveness of the front ends of the blades. The shroud ring is provided with an inner curved edge l3 which guides the air from the forwardly curved front ends l2 toward the outer edges of the blades. The axial flow produced by the front ends l2, if unrestricted, would tend to overload the rear ends of the blades. This tendency to overloading is decreased by the concave front faces and rearward inclination of the blades described above. This is apparent from Figs. 8 and 11. The axial flow produced by the forward end I2 is resisted by the curvature of the rear ends of the blades. The net result is that the air between the blades is kept at a more nearly uniform pressure and eddying between the blades is decreased. Eddylng is the source of noise.

It also decreases the 'efliciency of the fan blades- The outer edges III of the blades are inclined radially outward from the rear ends toward the front ends. In other words, the diameter of the fan increases from the rear toward the front. This increases the blade width at the front ends and makes the discharge from the blades more uniform throughout the length of the blades. The shape of the fan blades from the inner edges toward the outer edges along radial lines is shown in Figs. 9 and 10. The outer or discharge edges are substantially plane. The inner edges are curved forwardly with respect to the outer edges as regards the direction of rotation ofthe fan.- Intermediate the inner and outer edges the blades are slightly concave. From one aspect, the fan can be considered as a series of nozzles having a width measured by a line perpendicular to the front face of the blades and extending to the rear face of the adjacent blade. The shape is chosen so that the velocity of the air between the blades will be substantially constant at each radius. The forward curving of the inner edges of the blades provides a greater effective width between the blades which is necessary for the slower moving air at this point. The velocity of the air increases with the radius, and accordingly, less effective space is required. This decrease in space is effected by the change in inclination in the blades, and the width between the annular ring I and shroud ring 8.

The fan of the present'application is being claimed broadly in application Serial No. 82,780, filed June 1, 1936. The present application is directed to backwardly inclined blades.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a fan, axially extending blades having inner intake edges defining a passage into which air flows axially and outendischarge edges from which the air is discharged radially, the discharge edges being inclined backwardly as regards the direction of rotation of the fan, the blades being inclined in an axial direction rearwaidly as regards the direction of rotation of the fan from the rear toward the front ends, and the front ends of theblades being curved forwardly and projecting into the axially flowing air entering the fan and serving as scoops to increase the amount of air entering the fan.

2. In a fan, axially extending blades having inner intake edges defining a passage into which air flows axially and outer discharge edges from which the air is discharged radially, the discharge edges being inclined backwardly as regards the direction of rotation of the fan. the front faces of the blade being concave in an axial direction from the rear ends to the front ends along the inner and intermediate portions of the blades, and the front ends of the blades being curved forwardly and projecting into the axially flowng air entering the fan and serving as scoops to increase the amount of air entering the fan.

3. In a fan, axially extending blades having inner intake edges defining a passage into which air flows axially and outer discharge edges from which the air is discharged radially, the discharge edges being inclined backwardly as re gards the direction of rotation of the fan, the blades being inclined in an axialdirection rearwardly as regards the direction of rotation of the fan from the rear toward the ront ends, the inclination changing from the rear toward the front ends so asto produce concave front faces on the blade, and the front ends of the blades being curved forwardly and projecting into the axially flowing air entering the fan and serving as scoops to increase the amount of air entering the fan.

4. In a fan, a hub, a shroud ring, axially extending blades therebetween having inner intake edges radially inward from the shroud ring defining a passage into which air flows axially and outer discharge edges between the hub and the shroud ring from which air is discharged radially, the discharge edges being inclined backwardly as regards the direction of rotation of the fan, the front faces of the blades being concave in an axial direction from the rear toward the front ends, the front ends of the blades projecting within the inner edges of the shroud ring into the axially moving air entering the fan and serving to increase the amount of air entering the fan, and the shroud ring being curved to guide air from the front ends to the discharge edges of the blades.

5. In a fan, a hub, a shroud ring, axially extending blades therebetween having outer discharge edges between the hub and the shroud ring from which air is discharged radially and inner intake edges defining a passage into which air flows axially,.said inner edges being curved radially outward from the rear toward the front ends and terminating in forwardly curved front ends projecting beneath the inner edge of the shroud ring into the axially moving air entering the fan and serving as scoops to increase the amount of air entering the fan, the discharge edges being inclined backwardly as regards the direction of rotation of the fan, the front faces of the blades being concave in an axial direction from the rear toward the front ends, and the shroud ring being curved to guide air from the front ends to the discharge edges of the blades.

6. In a fan, axially extending blades having inner intake edges defining a passage into which air flows axially and outer discharge edges from which the air is discharged radially, the discharge edges being inclined backwardly as regards the direct-ion of rotation of the fan, the blades being inclined in an axial direction rearwardly as regards the direction of rotation of the fan from the rear toward the front ends, and

'the front faces of the blades being concave in a radial direction from the intake to the discharge edges.

'7. In a fan, a hub, a shroud ring, axially extending blades therebetween having inner intake edges radially inward from the shroud ring defining a passage into'which air fiows axially and outer discharge edges between the hub and the shroud ring from which air is discharged radially, the discharge edges being inclined backwardly as regards the direction of rotation of the fan, the front faces of the blades being concave in a radial direction from the intake to the discharge edges, the front ends of the blades projecting within the inner edges of the shroud ring into the axially moving air entering the fan and serving to increase the amount of air entering the fan, and the shroud ring serving to guide air from the front ends to the discharge edges of the blades.

8. In a fan, axially extending blades having outer discharge edges from which air is discharged radially, the discharge edges being inclined backwardly as regards the direction of rotation of the fan, the blades being inclined in an axial direction rearwardly as regards the direction of rotation of the fan from the rear toward the front ends, and the front faces of the blades being concave in a radial direction toward the discharge edges and in an axial direction from the rear toward the front ends.

KENTON D. MCMAHAN. 

